1. Field of the Invention
The present invention relates to a radio IC device and more particularly to a radio IC device for use in an RFID (Radio Frequency Identification) system. The present invention further relates to a radio communication terminal including a radio IC device.
2. Description of the Related Art
As an information management system for articles, an RFID system has recently been practiced which transfers predetermined information through communication in a non-contact manner by utilizing an electromagnetic field between a reader/writer generating an induction magnetic field and an RFID tag (also called a “radio IC device”) attached to an article. The RFID tag includes a radio IC element for storing predetermined information and processing a predetermined radio signal, and an antenna (a “radiator”) for transmitting and receiving a high-frequency signal. The RFID tag is used in a state attached to each of various articles (or packaging materials thereof) that are targets of management.
International Publications WO2009/011154 and WO2009/005080 disclose a radio IC device (RFID tag) in which radiation patterns each having a loop shape, when viewed from one direction, are coupled with a radio IC element. The radiation patterns couple a conductor, which functions as an antenna, with the radio IC element, whereby a dedicated antenna is not required and impedance matching is facilitated. However, because the radiation patterns have the loop shape only when viewed from one direction, a problem arises in that radiation directionality is changed depending on directions. Thus, the directionality lowers in the direction in which the radiation patterns appear in the loop shape.